Two pion decay of the Roper resonance

Hernández, E.; Oset, E.; Vacas, M. J. Vicente

doi:10.1103/physrevc.66.065201

Cited by 30 publications

(44 citation statements)

References 36 publications

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“…8. A similar behavior is also found in the calculations of [37,51]. The non-resonant part of the interaction kernel consists of the s-and u-channel nucleon Born terms and the t-channel pion exchange for the πN → σN transition, see diagram (i) in Fig.…”

Section: Isobar Contributions To Thesupporting

confidence: 58%

2πproduction in the Giessen coupled-channels model

2016

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The coupled channels Lagrangian approach underlying the Giessen model (GiM) is extended to describe the πN → πN , 2πN scattering in the resonance energy region. As a feasibility study we investigate single and double pion production up to the second resonance region. The 2πN production has been significantly improved by using the isobar approximation with σN and π∆(1232) in the intermediate state. The three-body unitarity is maintained up to interference pattern between the isobar subchannels. The scattering amplitudes are obtained as a solution of the Bethe-Salpeter equation in the K matrix approximation. As a first application we perform a partial wave analysis of the πN → πN , π 0 π 0 N reactions in the Roper resonance region. We obtain R σN (1440) = 27 +4 −9 % and R π∆ (1440) = 12 +5 −3 % for the σN and π∆(1232) decay branching ratios of N * (1440) respectively. The extracted πN inelasticities and reaction amplitudes are consistent with the results from other groups.

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Section: Isobar Contributions To Thesupporting

confidence: 58%

2πproduction in the Giessen coupled-channels model

2016

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“…Other works such as the Juelich model [21], which successfully describes the dynamical generation of the Roper resonance, contains additional information on the πN , π∆, ρN coupled channels and σN forces beyond the three body contact term of the chiral Lagrangians which we include here and which cancels the off-shell dependence of the amplitudes. An important contribution of the π∆ channel and ππ final state interaction (with one of the pions coming from the decay of the ∆ resonance) to the Roper resonance has also been claimed in [40]. Such information is not present in our formalism.…”

Section: Resultsmentioning

confidence: 80%

The N*(1710) as a resonance in the ππN system

2008

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We study the ππN system by solving the Faddeev equations, for which the input twobody t-matrices are obtained by solving the Bethe-Salpeter equation in the coupled channel formalism. The potentials for the ππ, πN sub-systems and their coupled channels are obtained from chiral Lagrangians, which have been earlier used to study resonances in these systems successfully. In this work, we find a resonance in the ππN system with a mass of 1704−i375/2 MeV and with quantum numbers I = 1/2, J π = 1/2 + . We identify this state with the N * (1710). This peak is found where the energies of the ππ sub-system fall in the region of the σ resonance. We do not find evidence for the Roper resonance in our study indicating a more complex structure for this resonance, nor for any state with total isospin I = 3/2 or 5/2. IntroductionThe excited states of the nucleon have been studied extensively theoretically as well as experimentally. This is evident from the fact that many of these states, especially those in the energy region below 1750 MeV, have been assessed either three or four stars by the particle data group (PDG) [1]. Even then, there are some resonances in this low energy region which still need unanimous agreement on their characteristics or existence, e.g., the J π = 1/2 + resonances in the isospin 1/2 domain. The N * (1440) or Roper resonance is a subject of continuous debate and the existence of the N * (1710) is even questioned. The quark models face difficulties in reproducing both these states [2,3,4]. In case of the N * (1710), some partial wave analyses [5,6] do not find any pole corresponding to it, while others claim a * kanchan@ific.uv.es † amartine@ific.uv.es ‡ oset@ific.uv.es 1 clear manifestation of this resonance [7,8,9,10]. On the other hand, the authors of [11] claim an indisputable existence of the N * (1710) from their study of the πN → ηN reaction in the coupled channel formalism and suggest that the status of this resonance should be improved from three-star to four-star.Another controversy about the N * (1710) started after the finding of a narrow peak in the γA → (K + n)X reaction at LEPS [12], suggesting the existence of a pentaquark state which some groups associated to a SU(3) antidecuplet to which the N * (1710) would also belong (see, for example, [13,14]). In order to be compatible with the Θ + , the N * (1710) is required to be narrow. However, the width of this resonance is not known precisely, with the widths listed in [1] ranging from ∼ 90 -480 MeV. The authors of [15] re-analyzed the πN → KΛ reaction and found that a narrow width of the N * (1710) [1] was incompatible with the data and proposed the existence of another narrow resonance in this energy region. The partial wave analyses group who do not find a pole for the N * (1710) suggested to look for other resonance in this energy region as a possible narrow, non-strange partner of the θ + [16,17]. The debate on this issue has continued with new analyses which do not find a signal for the θ + , as a consequence of which, the ca...

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“…An alternative interpretation of the Nππ decay is offered by Hernandez, Oset and Vicente-Vacas [51] who take into account the re-scattering of the two final state pions. The authors of [51] do not fit data; instead they show that they can reproduce qualitatively the phenomenology of N(1440)P 11 → Nππ decays by rescattering thus avoiding the need to introduce a genuine N(1440)P 11 → Nσ amplitude.…”

Section: Reactionmentioning

confidence: 99%